Psilochara acuta Grambast & Paul 1965

Psilochara aff. acuta Grambast & Paul, 1965

(Fig. 6 E-H)

Psilochara acuta Grambast & Paul, 1965: 243, pl. 2, fig. 5-9.

DISTRIBUTION. — Psilochara acuta has been recorded from many localities in Europe. In France, this species has been reported in the Lower Oligocene (Rupelian) of the Paris Basin (Riveline 1986). Schwarz (1997) recorded this species from the Oligocene of the Rhine Graben (Germany). Psilochara acuta was later reported from Upper Eocene (Priabonian) beds in the Transylvanian Basin, Romania by Baciu & Hartenberger (2001). Ŋe occurrence of this species in the Ebro Basin (Sarral locality) represents its southernmost record (Table 4). Riveline (1986) showed that the biostratigraphic range of this species encompasses three charophyte biozones i.e. Lychnothamnus pinguis, Lychnothamnus major and Chara microcera. However, the occurrence of this species within the European Harrisichara vasiformis-tuberculata biozone in the Transylvanian Basin and within the Lychnothamnus vectensis biozone in the Ebro Basin suggests that the occurrence of Psilochara aff. acuta starts in the middle part of the Priabonian.

DESCRIPTION

Gyrogonites small to medium, 360-549 µm high (mean 478 µm) and 280-450 µm wide (mean 327 µm), prolate and elongate in shape, with an isopolarity index ranging from 103-184 (mean 147). Spiral cells flat to concave, about 53 µm wide and without ornamentation. Eight to ten (frequently nine) convolutions are visible in lateral view. Apex psilocharoid and prominent, frequently pointed. Ŋis apical cap is very variable in size, ranging between 15 and 77 µm in high. Base rounded in well-calcified gyrogonites and slightly pointed in poorly calcified gyrogonites, showing a small pentagonal pore (about 40 µm in diameter).

REMARKS

Ŋe main difference between the population from Sarral (NE Ebro Basin) and the type material from Soisy-sur-École (Paris Basin) is the size of the gyrogonites, which is about 250 µm smaller in the Ebro Basin. Moreover, gyrogonites from the type population display a larger range of convolutions (eight to twelve).